The electron microscopy of post-growth induced defects of ZnSe/GaAs epilayers |
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Authors: | J E Yu K S Jones |
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Affiliation: | (1) Department of Materials Science and Engineering, University of Florida, 32611 Gainesville, FL, USA |
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Abstract: | A fundamental research of structural defects induced upon post-growth processing of ZnSe/GaAs epilayers grown on (100) GaAs
was done by identifying defect-related reflections in the transmission electron diffraction (TED) patterns of ZnSe. Structural
artifacts, other than the as-grown defects, on this material system could be excluded according to our results. Four types
of abnormal reflections have been observed in addition to primary reflections. These extra reflections are sensitive to the
post-growth processing of ZnSe epilayers and may arise from various external effects, rather than epitaxy growth, such as
irradiation damage, surface oxidation, and surface contamination. By mapping these reflections at several major zone axes
using TED patterns, we found that the reciprocal lattice for a ZnSe crystal with structural defects consists of two distinct
types of extra reflections associated with irradiation damage. The first type of extra reflections is ±1/3{111} and the other
is ±1/2{111} corresponding to pure-edge and non-edge dislocation loops, respectively. For (100) oriented wafers, the ±1/3{111}
and ±1/2{111} reflections were observed only on two of the four possible 〈111〉 variants (i.e. 111]Zn and 111]Zn)and this phenomenon was attributed to the anisotropy of defect distribution. Extra reflections associated with surface oxidation
and contamination are also observed. The orientation relationships between a surface hexagonal ZnO and a cubic ZnSe film are
0001]ZnO//−111]ZnSe, and 01−11]ZnO//011]ZnSe. The origin, characterization, and elimination of these induced reflections are discussed. With the knowledge about these
extra effects on structural defect formation, we have shown the real microstructure of ZnSe epilayers. |
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Keywords: | Irradiation damage thin films transmission electron miscroscopy ZnSe |
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